Reduce The Disk Size On Vios Client Lpar

I've created a new LV with size of 100GB on VIOS and map it to client LPAR for rootvg disk.
After AIX OS installation and configuration done in client LPAR ,suddenly I need to reduce the disk size from 100GB to 20GB. Any impact on client rootvg if I just reduce the disk size concurrently ? Or do I need to reconstruct the disk and perform a fresh AIX installation on client Lpar.

I am not sure this operation you want to exec is safe. So why you do not create new disk for this LPAR, attach it to LPAR, in LPAR add it in rootvg, move all LV to the new disk, create boot record on new disk and then reduce rootvg with this 100GB disk.

First, Its not easy to reduce the size of a raw lv[With out fs on it], and the rootvg for your client is LV mapped from VIOS.
You can use lreducelv with map files but thats a hard way and you dont know which pps are free.
Its better to follow Romeo's suggestion.

If you are looking for the safest way to do it, go with what Romeo suggested originally and others agreed. I don't think you can even reduce the size of the LV withouth having to kill the LPAR that is using it as a rootvg disk first. You should get an error in VIO server saying the device is busy.
Interesting question though.